The first observation of about 2000 candidates, with a background contamination below 3%, of the rare decay K± → φ± φ0e+e- is reported by the NA48/2 experiment. The preliminary branching ratio in the full kinematic region is obtained to be: B(K± → φ±φ0e+e-) = (4.06 ± 0.17) • 10-6 by analyzing the data collected in 2003. A sample of 4.687×106 K± → φ±φ0D,decay candidates with a negligible background contamination collected in 2003-04 is analyzed to search for the dark photon (A') via the decay chain K± → φ± φ0, φ0 → γA',A'→e+e-. No signal is observed, and preliminary limits in the plane dark photon mixing parameter η2 vs. its mass mA' are reported.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Physics and Astronomy (miscellaneous)